Continuous Plankton Records: Seasonal cycles of phytoplankton and copepods in the North Atlantic ocean and the North Sea

Abstract

Data from the Continuous Plankton Recorder survey of the north AtlanticOcean and the North Sea were used to study geographical variationsin the amplitude, duration and timing of the seasonal cycles of totalphytoplankton and total copepods. It is shown that the distributionof overwintering stocks influences the distributions throughout theyear. There is a relationship between the timing of the spring increaseof phytoplankton and the amplitude of the seasonal variation in seasurface temperature. In the open ocean, the timing of the springincrease of phytoplankton corresponds with the spring warming ofthe surface waters. In the North Sea the spring increase occurs earlier,associated, perhaps, with transient periods of vertical stability,resulting in a relatively slower rate of increase. It is suggestedthat in the open ocean the higher rate of increase is under-exploitedby copepods due to low overwintering stocks and longer generationtimes. Exceptionally early spring increases of phytoplankton offthe west coast of Greenland and over the Norwegian shelf are probablyassociated with permanent haloclines. A high and late autumn peakof phytoplankton off the coast of Portugal may be associated withcoastal upwelling.